Effect of substrate temperature in chloroaluminum phthalocyanine thin films deposition studied by scanning tunneling microscopy and tunneling spectroscopy

Abstract The AlPcCl films deposited on a KCl substrate at two different substrate temperatures ( T s , −120°C and 180°C) with the average film thickness of 100 nm were investigated using scanning tunneling microscopy (STM) and tunneling spectroscopy (TS). The films were transferred onto HOPG in order to make STM and TS measurements possible. The STM as well as the electron diffraction measurement exhibited the amorphous and crystalline structures for T s of −120°C and 180°C, respectively. The potential region with low conductance (conductance well) in the d I /d V curve was smaller ( T s , −120°C) and larger ( T s , 180°C) when compared with the band gap value of the AlPcCl film ( T s , 180°C) which we previously evaluated from the optical absorption measurement. We estimated the band bending with the assistance of the carrier concentration obtained from the ESR measurement. It is supposed that the electronic states created within the band gap caused the vanishing of band bending change for T s of −120°C, leading to the decrease of conductance well. On the other hand, the band bending was found to be crucial for T s of 180°C, which possibly resulted in the widening of conductance well.